Messier 21: Difference between revisions
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M21 is a relatively young cluster of a mere 4.6 million years of age. It is tightly packed but contains about 57 stars. A few blue giant stars have been identified in the cluster, but Messier 21 is composed mainly of small dim stars. With a magnitude of 6.5, M21 is not visible to the naked eye; however, with the smallest binoculars it can be easily spotted on a dark night. | M21 is a relatively young cluster of a mere 4.6 million years of age. It is tightly packed but contains about 57 stars. A few blue giant stars have been identified in the cluster, but Messier 21 is composed mainly of small dim stars. With a magnitude of 6.5, M21 is not visible to the naked eye; however, with the smallest binoculars it can be easily spotted on a dark night. | ||
<ref>[http://en.wikipedia.org/wiki/Messier_21 Messier 21]</ref> | <ref>[http://en.wikipedia.org/wiki/Messier_21 Messier 21]</ref> | ||
==HGS Session References== | |||
HGS Sessions - Clearing [[Macau Island, China]] - 3/21/2015 <ref>HGS Session</ref> | |||
Revision as of 22:34, 21 March 2015
Messier 21 or M21 (also designated NGC 6531) is an open cluster of stars in the constellation of Sagittarius. It was discovered and catalogued by Charles Messier on June 5, 1764. M21 is a relatively young cluster of a mere 4.6 million years of age. It is tightly packed but contains about 57 stars. A few blue giant stars have been identified in the cluster, but Messier 21 is composed mainly of small dim stars. With a magnitude of 6.5, M21 is not visible to the naked eye; however, with the smallest binoculars it can be easily spotted on a dark night. [1]
HGS Session References
HGS Sessions - Clearing Macau Island, China - 3/21/2015 [2]
References
- ↑ Messier 21
- ↑ HGS Session
Found in HGS Manual on Page 108
Found in HGS Manual on Page 115